I take it that since your tape drives are on a SAN, they are being 
shared by multiple hosts?  The "external event caused rewind" suggests 
that while one server was performing a backup, another host that can see 
the drives did a SCSI inquiry or some other command to the drive which 
caused it to rewind in the middle of the backup.  Do you have your media 
server set up to use SCSI RESERVE?  We had a very similar problem to 
what you describe with NBU 3.4 up until patch 4.

If you're not familiar with what the SCSI RESERVE does, here's a brief 
description...when a host opens the device and issues a SCSI RESERVE 
command, the drive will respond only to commands issued by the HBA that 
did the SCSI RESERVE.  If another HBA tries to access the device with 
the reserve, it will get an error along the lines of "device busy".  
This prevents hosts in a SAN from interfering with each other.

Now, even if you're using SCSI RESERVE (it should be on by default in 
4.5+), if another process on the host that is already using the tape 
drive tries to do something with the drive, it can still interfere with 
the backup.  Are there any other processes on the server that could be 
trying to access the tape drive at the same time as the backup is running?

Also, windows is notorious for assuming that it is the only server who 
is using shared devices, and it acts accordingly.  Our windows admins 
had to turn off something in  their servers to stop it from probing the 
tape devices every minute.

Eric Ljungblad wrote:

>Keep in mind that that the tape device drivers Are sending you these messages 
>- since we made it past the loader we should look at the drivers on the drives 
>or the firmware - should have firmware 1.07 or better on the drives and , up 
>to date drivers. Veritas offers some OK drivers on there install CD under 
>additional products, tape device drivers, install them, reboot then use 
>robtest to test drives?
>If you can initialize a tape in the robot from your gui then backups are hot / 
>good 
>Eric
>
>________________________________
>
>From: veritas-bu-admin AT mailman.eng.auburn DOT edu on behalf of ida3248b AT 
>post.cybercity DOT dk
>Sent: Mon 1/16/2006 12:54 AM
>To: veritas-bu AT mailman.eng.auburn DOT edu
>Subject: [Veritas-bu] Periodic status 84 on IBM 3584 with LTO3
>
>
>
>Hello All
>
>We have an IBM 3584 with LTO3 drives SAN attached to a windows 2003 server.
>
>We're getting status 84 with external event caused rewind
>
>We havn't been able to find anything in the logs
>
>Any ideas/suggestions will be appriecated
>
>Regards
>Michael
>
>--
>Cybercity Webhosting (http://www.cybercity.dk)
>
>_______________________________________________
>Veritas-bu maillist  -  Veritas-bu AT mailman.eng.auburn DOT edu
>http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu
>
>
>
>  
>


-- 
Jack L. Forester, Jr.
UNIX Systems Administrator, Stf
Lockheed Martin Information Technology
(304) 625-3946